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clang-sys

Crate Documentation CI MSRV

Rust bindings for libclang.

If you are interested in a somewhat idiomatic Rust wrapper for these bindings, see clang-rs.

Released under the Apache License 2.0.

Documentation

Note that the documentation on https://docs.rs for this crate assumes usage of the runtime Cargo feature as well as the Cargo feature for the latest supported version of libclang (e.g., clang_16_0), neither of which are enabled by default.

Due to the usage of the runtime Cargo feature, this documentation will contain some additional types and functions to manage a dynamically loaded libclang instance at runtime.

Due to the usage of the Cargo feature for the latest supported version of libclang, this documentation will contain constants and functions that are not available in the oldest supported version of libclang (3.5). All of these types and functions have a documentation comment which specifies the minimum libclang version required to use the item.

Supported Versions

To target a version of libclang, enable a Cargo features such as one of the following:

  • clang_3_5 - requires libclang 3.5 or later
  • clang_3_6 - requires libclang 3.6 or later
  • etc...
  • clang_17_0 - requires libclang 17.0 or later
  • clang_18_0 - requires libclang 18.0 or later

If you do not enable one of these features, the API provided by libclang 3.5 will be available by default.

Note: If you are using Clang 15.0 or later, you should enable the clang_15_0 feature or a more recent version feature. Clang 15.0 introduced a breaking change to the EntityKind enum which resulted in a mismatch between the values returned by libclang and the values for EntityKind defined by this crate in previous versions.

Dependencies

By default, this crate will attempt to link to libclang dynamically. In this case, this crate depends on the libclang shared library (libclang.so on Linux, libclang.dylib on macOS, libclang.dll on Windows). If you want to link to libclang statically instead, enable the static Cargo feature. In this case, this crate depends on the LLVM and Clang static libraries. If you don't want to link to libclang at compiletime but instead want to load it at runtime, enable the runtime Cargo feature.

These libraries can be either be installed as a part of Clang or downloaded here.

Note: The downloads for LLVM and Clang 3.8 and later do not include the libclang.a static library. This means you cannot link to any of these versions of libclang statically unless you build it from source.

Versioned Dependencies

This crate supports finding versioned instances of libclang.so (e.g.,libclang-3.9.so). In the case where there are multiple instances to choose from, this crate will prefer instances with higher versions. For example, the following instances of libclang.so are listed in descending order of preference:

  1. libclang-4.0.so
  2. libclang-4.so
  3. libclang-3.9.so
  4. libclang-3.so
  5. libclang.so

Note: On BSD distributions, versioned instances of libclang.so matching the pattern libclang.so.* (e.g., libclang.so.7.0) are also included.

Note: On Linux distributions when the runtime features is enabled, versioned instances of libclang.so matching the pattern libclang.so.* (e.g., libclang.so.1) are also included.

Environment Variables

The following environment variables, if set, are used by this crate to find the required libraries and executables:

  • LLVM_CONFIG_PATH (compiletime) - provides a full path to an llvm-config executable (including the executable itself [i.e., /usr/local/bin/llvm-config-8.0])
  • LIBCLANG_PATH (compiletime) - provides a path to a directory containing a libclang shared library or a full path to a specific libclang shared library
  • LIBCLANG_STATIC_PATH (compiletime) - provides a path to a directory containing LLVM and Clang static libraries
  • CLANG_PATH (runtime) - provides a path to a clang executable

Linking

Dynamic

libclang shared libraries will be searched for in the following directories:

  • the directory provided by the LIBCLANG_PATH environment variable
  • the bin and lib directories in the directory provided by llvm-config --libdir
  • the directories provided by LD_LIBRARY_PATH environment variable
  • a list of likely directories for the target platform (e.g., /usr/local/lib on Linux)
  • macOS only: the toolchain directory in the directory provided by xcode-select --print-path

On Linux, running an executable that has been dynamically linked to libclang may require you to add a path to libclang.so to the LD_LIBRARY_PATH environment variable. The same is true on OS X, except the DYLD_LIBRARY_PATH environment variable is used instead.

On Windows, running an executable that has been dynamically linked to libclang requires that libclang.dll can be found by the executable at runtime. See here for more information.

Static

The availability of llvm-config is not optional for static linking. Ensure that an instance of this executable can be found on your system's path or set the LLVM_CONFIG_PATH environment variable. The required LLVM and Clang static libraries will be searched for in the same way as shared libraries are searched for, except the LIBCLANG_STATIC_PATH environment variable is used in place of the LIBCLANG_PATH environment variable.

Note: The libcpp Cargo feature can be used to enable linking to libc++ instead of libstd++ when linking to libclang statically on Linux or Haiku.

Static Library Availability

Linking to libclang statically on *nix systems requires that the libclang.a static library be available.
This library is usually not included in most distributions of LLVM and Clang (e.g., libclang-dev on Debian-based systems).
If you need to link to libclang statically then most likely the only consistent way to get your hands on libclang.a is to build it yourself.

Here's an example of building the required static libraries and using them with clang-sys:

git clone git@github.com:llvm/llvm-project.git
cd llvm-project

cmake -S llvm -B build -G Ninja -DLLVM_ENABLE_PROJECTS=clang -DLIBCLANG_BUILD_STATIC=ON
ninja -C build

cd ..
git clone git@github.com:KyleMayes/clang-sys.git
cd clang-sys

LLVM_CONFIG_PATH=../llvm-project/build/bin/llvm-config cargo test --features static

Linking to libclang statically requires linking a large number of big static libraries.
Using rust-lld as a linker can greatly reduce linking times.

Runtime

The clang_sys::load function is used to load a libclang shared library for use in the thread in which it is called. The clang_sys::unload function will unload the libclang shared library. clang_sys::load searches for a libclang shared library in the same way one is searched for when linking to libclang dynamically at compiletime.